CVE-2026-79611

Name	CVE-2026-79611
Description	For XSA-308 logic was introduced, as VMX VMEntry checks do not like the exact combination of state which occurs when #DB in intercepted, Single Stepping is active, and blocked by STI/MovSS is active, despite this being a legitimate state to be in. The resulting VMEntry failure is fatal to the guest. Sadly there is another special sub-case of the above, with branch tracing enabled. In that case the prior adjustment would still cause a VMentry failure, as before fatal to the guest.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DSA-6571-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
xen (PTS)	bookworm	4.17.5+72-g01140da4e8-1	vulnerable
	bookworm (security)	4.17.7-0+deb12u1	vulnerable
	trixie	4.20.3+127-gc42374a105-0+deb13u1	vulnerable
	trixie (security)	4.20.4+39-gf1e1321c87-0+deb13u1	fixed
	forky	4.20.3+127-gc42374a105-1	vulnerable
	sid	4.20.4+39-gf1e1321c87-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
xen	source	trixie	4.20.4+39-gf1e1321c87-0+deb13u1		DSA-6571-1
xen	source	(unstable)	4.20.4+39-gf1e1321c87-1

https://xenbits.xen.org/xsa/advisory-518.html